Project Summary Sepsis is a life-threatening disease with high morbidity and mortality. New therapeutic strategies are urgently needed to treat this devastating disease. Uncontrolled endothelial inflammatory responses, which often leads to inflammatory vascular injury, contribute to the pathogenesis of multiple organ failure in sepsis. HDAC6, a histone deacetylase, has been reported to modulate nuclear and non-nuclear protein function through deacetylation. In this project, we will investigate HDAC6 regulation of endothelial inflammatory injury during sepsis. In our preliminary studies, we demonstrated that HDAC6 knockdown or selective HDAC6 inhibition prevented TNF-? induced endothelial ICAM-1 expression, which was associated with increased ?-tubulin acetylation and reduced STAT1 activation. Furthermore, in mouse models of sepsis, HDAC6 inhibition blocked sepsis-induced lung ICAM-1 expression, induced ?-tubulin acetylation, and suppressed STAT1 activation in lung tissues, which was associated with reduced lung inflammatory injury and increased survival rate. In the proposed studies, we will conduct a serial of experiments to assess the role of HDAC6 in sepsis-induced endothelial inflammatory responses, and to investigate therapeutic mechanisms of HDAC6 inhibition against endothelial inflammatory signaling in sepsis.